Sigma function

The Sigma function is the function of Summation. Summation is the iterable addition of something.

This is an example of a Sigma function. The function can be interpreted as follow: The variable above the Sigma, n, is the upper bounds of the iteration; once the iterate variable, k, reaches the upper boundary the iteration stops. The value k changes in increments of one until it reaches the upper boundary, the value you plug in for the function is the current value of k. The value of k represented at the bottom of the Sigma function is the lower boundary, it is the value that you start the incremental count at. For a summation function you just then plugin the current value of k starting at k until k = n and add up the results of the results of each function calculation.